1. Field of the Invention
The present invention relates to a sliding member. More particularly, the present invention relates to a sliding member which is provided with micropores on the sliding surface thereof, thereby having a novel structure and improving the sliding characteristics under such severe sliding conditions as a high sliding speed, a high surface pressure, and a small amount of lubricating oil, so that the seizure resistance and the seal property of the sliding member are considerably enhanced.
2. Description of the Prior Art
The main trend in the development of sliding members has been to improve the material and structure of such members. Recently, a few proposals have been made to subject sliding members to surface treatment so as to improve their sliding characteristics.
Japanese Unexamined Patent Publication No. 51-74153/76 proposes that bearing material for use as a thrust washer be surface-roughened and then subjected to anode oxidation so as to form an uneven surface and so as to retain lubricating oil in the concave portions of such a surface.
Japanese Unexamined Patent Publication No. 48-100541/73 proposes to improve the sliding characteristics of a slide bearing by means of shot blasting.
Japanese Unexamined Patent Publication No. 56-131861/81 proposes to electrolytically deposit chromium on either a stationary member or a movable member of a mechanical seal or both so as to improve the seal property thereof.
According to the prior art for surface-treating sliding members, the degree of surface treatment or the structure of the micropores is mainly defined by the maximum height R.sub.max and the average roughness of ten points R.sub.z and is occasionally defined by the diameter of the micropores or the number of micropores per unit area. The R.sub.max and the like are measured with a conventional roughness tester.
Recently, a measuring device, which is referred to as a particle counter or a particle analyzer, has been put to practical use. The particle counter or particle analyzer involves a principle, according to a catalogue published by the Japanese corporation "LUZEX", that an image of particles is detected by a microscope and is converted to a video signal by means of a television camera. The image of the particles is then transmitted to a shade-correcting circuit, and a nonuniform brightness resulting from nonuniform lighting by the microscope and the nonuniform sensitivity of the television camera is corrected, thereby rendering the image of the particles uniformly bright. The image of the particles is then transmitted to a threshold circuit, from which the image of the particles to be measured is extracted and is converted to a binary image. That is, the image of the particles to be measured and the image of the particles not to be measured are completely separated by their densities in the threshold circuit. The binary image is transmitted to a counter circuit, in which the image of the particles included in a frame for determining the measuring field is selected. The thus-selected image of the particles is measured with regard to the number, area, and intersections thereof, as well as the area of the frame. By means of the above-described particle counter or the like, it is possible to accurately measure the number, area, average area, intersections, particle-diameter distribution, and the like any kind of particles, even particles which cannot be measured by means of a conventional roughness tester or the like.